EzPAP^® Positive Airway Pressure Device

DHD Healthcare

Wampsville, NY

August 26, 1999

CITECH #490-370

Typical Medical Device Testing Report

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Report approved by: Robert Mosenkis, P.E., President

Date: August 26, 1999

CITECH (Center for Information on Technology for Health Care) is an independent testing organization that serves the medical device industry. CITECH provides testing of safety and performance based on extensive knowledge of a broad range of medical devices. CITECH is accredited by FDA as a third-party reviewer of eligible 510(k) submissions. It is endorsed by ECRI, the world's largest independent evaluator of healthcare technology, and by hospitals and other agencies worldwide. CITECH shares with ECRI a 120,000-square-foot suburban Philadelphia facility that includes extensively instrumented laboratories for electronic, environmental, mechanical, and physical testing.

Summary

DHD Healthcare contracted with CITECH to conduct testing of its EzPAP^® positive airway pressure device. We were asked to simulate a spontaneously breathing patient and demonstrate the ability of the device to provide positive airway pressure during inspiration and breath pause, as well as during exhalation, across a range of breathing conditions. In clinical use, the EzPAP device is attached to a mouthpiece, through which the patient breathes. One port on the device provides connection to a source of compressed gas (either air or oxygen), while a second port allows the pressure to be sensed. Air or oxygen flow is adjusted to provide the desired positive pressure levels, as measured through the sensing port.

We used a two-section test lung to simulate the patient. We drove one section of the lung with a ventilator and coupled the second section of the lung to the first, so that it would "inhale" and "exhale" at the same respiration rate and inspiration time. We connected the EzPAP device to the second section of the lung. We monitored the gas flow through the EzPAP device, as well as the pressure at its sensing port and oxygen concentration in the test lung, through an automated data acquisition system. We connected the gas inlet port of the device to an oxygen cylinder through a regulator and flowmeter.

By adjusting the ventilator and the resistance and compliance of the test lung, we set various combinations of I:E ratios from 1:1 to 1:3 (where I:E was the ratio of inspiratory to expiratory flow times, excluding the pause between breaths) and peak expiratory flows of 5 to 40 L/min. We adjusted the oxygen flow to the EzPAP device to provide expiratory pressures of either 10 or 20 cmH₂O. For each of 36 parameter sets, we recorded and graphed pressure and flow, and we calculated average oxygen concentration in the lung. One typical graph is included in this Summary. [All graphs were presented in the body of the original report, but the other 35 are omitted from this Website version.] We did complete testing on one sample of the EzPAP device, and spot checks on two others. While performance was not identical for all samples, they were all capable of providing positive airway pressure throughout the breathing cycle.

The results demonstrated that, except for a few conditions of high inspiratory flow, the EzPAP device was capable of providing positive airway pressure during all phases of the breathing cycle. CITECH can draw no conclusions regarding the clinical significance of these results.

Testing was done using a Michigan Instruments Vent Aid TTL training test lung to simulate a spontaneously breathing patient. The lung has two sections, and it can be configured such that the second section can be driven by the first; that is, when the first section of the lung inflates, a coupling bar forces the second section to expand, as well. For exhalation, the second section can deflate, based on its compliance and resistance, no faster than the first section.

We used an Aequitron LP6 ventilator to drive the first section of the lung, and set the respiration rate to 15 breaths/min throughout our testing. To the inlet of the second section of the lung, we attached the EzPAP device in series with an adjustable orifice (to vary the airway resistance). Also in series with the EzPAP device was an electronic pneumotach, which measured the instantaneous flow through the EzPAP device. We connected the fresh gas port of the device, through a 0-15 L/min flowmeter, to an H-tank of oxygen. An oxygen sensor was placed in the test lung to monitor oxygen concentration. The oxygen sensor, as well as a sensing line from the pressure port of the EzPAP device and the output of the pneumotach, were all connected to a microprocessor-based data acquisition system that recorded values 100 times per second. All test equipment was selected as being appropriate for the purpose and was calibrated either at the time of use or as part of a routine periodic inspection program.

For all combinations of peak expiratory flows of 5, 10, 15, 20, 30, and 40 L/min and I:E ratios of 1:1, 1:2, and 1:3, we were asked to adjust the oxygen flow to provide peak expiratory pressures of 10 and 20 cmH₂O (all values approximate). The various parameter sets were obtained by adjusting the settings on the ventilator that drove the test lung, the resistance in series with the EzPAP device, and the compliance of the lung. The I:E ratio was defined as the ratio of the inspiratory flow time to the expiratory flow time, excluding the pause between breaths. For each set of parameters, we collected data to provide graphs of pressure and flow at the EzPAP device and to calculate average oxygen concentration in the test lung (the oxygen concentration was averaged over one breathing cycle). We also recorded the oxygen flowmeter reading.

Because our data acquisition system collected 100 data points a second and had a very fast response time, the first graphs we produced showed considerable rapid, low-amplitude "chatter", possibly caused by flow turbulence in the EzPAP device. These fluctuations were too fast to have any physiological effect, so the patient would not notice them. To make the graphs clearer, we used data averaging to smooth them out; we averaged the pressure or flow value at the instant under consideration with 8 values immediately preceding it and 8 values immediately following it. [Where 8 data points were not available (i.e., at the very beginning and end of the data collection interval), we averaged as many points as were there.] The graphs presented in this report reflect this data smoothing.

We gathered complete data on one sample of the EzPAP device, and ran spot checks on two other samples.

Results of the tests are provided as pressure and flow graphs for each parameter set and as a table of average oxygen concentrations for each set of parameters. Each graph also lists the oxygen flow needed to obtain the 10 or 20 cmH₂O peak expiratory airway pressure (the flowmeter was read to the nearest 0.5 L/min). [One set of data, for peak expiratory flow of 40 L/min, I:E of 1:2, and PAP of 20 cmH₂O, is omitted because of a data acquisition error.] The graphs demonstrate that the EzPAP device was able to maintain positive airway pressure throughout the ventilatory cycle, except in a few conditions of high peak inspiratory flow.

Average oxygen concentrations are listed in the following table. [Of course, these values are valid only when the EzPAP is connected to a source of compressed oxygen, rather than air.]

Average Oxygen Concentrations in Lung

* Data collection error

We checked the performance of two other EzPAP samples by substituting them in the test circuit, for each of three parameter sets, without making any changes in the ventilator or flow resistance. While performance was not identical for each sample, each provided positive pressure throughout the breathing cycle.

We conclude that the EzPAP, under nearly all conditions, is able to provide adjustable positive airway pressure during all phases of the breathing cycle.